The invention relates to a watertight housing of an apparatus, for example an electrically chargeable shaver, which housing is provided with at least one opening in a wall, which opening is closed off by a foil, said foil rendering possible a pressure equalization in the housing with respect to the outer atmosphere.
The invention further relates to a watertight housing of an apparatus, for example an electrically chargeable shaver, wherein in the housing a separate battery compartment is present for accommodating rechargeable cells or batteries, which battery compartment is provided with at least one opening in a wall, which opening is closed off by a foil which renders possible the escape of gases generated during charging of the batteries from the battery compartment to the outer atmosphere.
The invention further relates to a battery compartment for accommodating rechargeable cells or batteries, for example for use in an apparatus, for example an electrically chargeable shaver, which compartment is provided with at least one opening in a wall, which opening is closed off by a foil which renders possible the escape of gases generated during charging of the batteries from the battery compartment to the outer atmosphere.
Since various devices, for example electrically chargeable shavers, electric toothbrushes and the like are used in humid rooms, such as a bathroom, such devices should be at least splash-proof for reasons of safety. Seals have been provided for this purpose in the housing in suitable locations, for example on the connection seams of the various housing parts or at the areas of certain components such as shaver heads, switches, collectors, etc.
A pressure difference may arise between the interior of the housing and the outer atmosphere owing to temperature differences, for example owing to cleaning of such an apparatus under a hot tap. The resulting pressure difference may damage the seals mentioned above, so that the apparatus is no longer watertight, which is undesirable in view of the safety risks.
To equalize such pressure differences without damage to the seals in a simple and most of all fast manner, one or several openings are provided in the housings of present-day devices of the type mentioned above, which openings are screened off by a gas-transmitting foil, for example of the watertight Gore-Tex(copyright) type. The term foil denotes a flexible layer of any material such as, for example, rubber or synthetic resin.
Such watertight, gas-transmitting foils are also used in battery compartments which are present in the housings of electrically chargeable devices. An example of such an application is disclosed in the international patent application No. PCT/US 95/01054 published under No. WO 96/08048.
In such an application, the foil serves to provide a possibility for gases to escape, in particular explosive hydrogen gas H2 which is generated during charging of the batteries at the area of the positive electrode and accordingly creates an undesirable overpressure in the battery compartment.
Next to the fact that such materials are comparatively expensive, such xe2x80x9cbreathingxe2x80x9d foils are highly sensitive to pollution, owing to which the gas-transmitting pores of the foil are choked up in the course of time, and the foil accordingly loses its xe2x80x9cbreathingxe2x80x9d function. In addition, such foils transmit gas in one direction only, which limits their pressure equalization function.
The invention has for its object to provide a pressure equalization means for use in apparatuses of the kind mentioned above which are not only insensitive to pollution but are also capable of equalizing a plurality of pressure differences.
To achieve this object, the foil is elastically deformable and provided with at least one continuous incision whose cutting edges can yield under the influence of a pressure difference obtaining across the foil. Since the opening in the foil does not open until a pressure difference is present, it cannot become contaminated and choked up during normal use.
In addition, pressure equalization can now take place in two directions with such a mechanically deformable foil. Both an overpressure and an underpressure can be equalized with respect to the outer atmosphere, which is highly desirable in view of the service life of the apparatus and which cannot be achieved by foils which equalize pressures in one direction only.
The pressure at which the incision in the foil opens can be influenced by the choice of a mechanically deformable foil. This opening pressure is influenced not only by the material properties of the foil, but constructional properties also play a part. Since the operational surface areas of the foil in the region of the opening are mutually unequal in an embodiment of the invention, the required opening pressure for an overpressure may be different from the required opening pressure for an underpressure in the housing or battery compartment, and may in addition be adjustable.
In more specific embodiments according to the invention, the incision in the foil may be a straight or a curved incision.